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ACRS Humanes 2013

Adriana Humanes
September 24, 2016
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ACRS Humanes 2013

Adriana Humanes

September 24, 2016
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  1. Effects of turbidity and sedimentation on the
    survival of Pocillopora damicornis recruits
    Adriana Humanes, Katharina Fabricius, Bette Willis, Andrew Negri

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  2. Introduction
    Buddemeier et al. 2004, Hutchings & Haynes 2005, Hutchings et al.2005, Hoegh-Gulberg et al. 2007
    Stressors on coral reefs

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  3. Runoff and coral reefs:
    Introduction
    Sediments and nutrient input in the Great
    Barrier Reef Lagoon have increased since 1823:
    Sediment - x 5.5
    Nitrogen- x 5.7
    Phosphorus - x 8.9
    Kroon et al. 2012
    Mitchell et al. 1997, 2001, Tilman et al. 2001, Smith et al. 2003, Devlin & Brodie 2005, Fabricius 2011

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  4. Sediments and early life histories of corals
    Fine sediments will stay suspended and…
    Introduction
    Organic
    Carbon,
    Nitrogen
    Phosphorous

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  5. Sediments and early life histories of corals
    Fine sediments will stay suspended and…
    Introduction
    Residence time of fine sediments, N and P: years to decades in
    the GBR lagoon
    All coral life history stages submitted to enriched sediments
    Kroon et al. 2012, Fabricius et al. 2013, Brodie et al. 2013

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  6. Smothered
    Sed
    Fabricius et al. 2003
    Control Nut Sed + Nut
    Mortality (%)
    Introduction
    Coral spat survivorship under sediment stress:
    Tolerance to
    sediments
    At least 1 order of
    magnitude lower
    Fabricius 2005

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  7. Objective
    To measure the survivorship
    of β-Pocillopora damicornis
    recruits exposed to
    1) three turbidity levels for 31
    days.
    2) sedimentation at several
    levels of organic enrichment.

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  8. Experiment 1: Effects of suspended sediments on recruit survivorship
    Sediments collected in Orpheus
    and sieved ˂63 µm
    2 weeks
    0 mg/l
    124
    30 mg/l
    110
    100 mg/l
    111

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  9. Water sample analysis:
    • Total suspended solids
    Data analysis:
    SDR: Anova
    SAR: Kruskal-Wallis
    Recruit’s size and # polyps: Kruskal-Wallis
    Survivorship: Kaplan-Meir
    Data
    Size:
    Maximum diameter
    # of polyps
    Survivorship rate:
    % recruits alive after 31 days
    • Sedimentation deposition rates (SDR)
    • Sediment attachment rate (SAR)
    • Nitrogen, Phosphorus and Carbon
    • Pigments
    • Bacterial community (454 sequencing)
    Experiment 1: Effects of suspended sediments on recruit survivorship

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  10. N.S.
    Number of polyps/recruit
    p<0.05
    Recruits size (mm)
    0.9
    1
    1.1
    1.2
    1.3
    *
    Experiment 1: Effects of suspended sediments on recruit survivorship
    • Turbidity reduces energy for growth
    • Clearing sediments is energetically
    costly (mucus production: 2.5 x more expensive
    than other physiological functions; Riegl & Branch
    1995)
    • Trade-off between growth and
    maintenance
    Recruits size

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  11. Experiment 1: Effects of suspended sediments on recruit survivorship
    p<0.05
    Differences
    after 18 days
    30 mg/l is as lethal as 100 mg/l for coral recruits of Pocillopora damicornis
    Survivorship (%)
    100
    80
    60
    40
    20
    0
    0 5 10 25 30
    Time (days)
    15 20

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  12. 10
    larvae
    559
    recruits
    Sediments collected in
    Orpheus and sieved ˂63 µm
    Incubation: 24 h
    Sedimentation: 1h approximately
    4 enrichment levels
    Sample times:
    3, 6, 12, 24, 48 h
    5 vials
    Experiment 2: Effects of organically enriched sedimentation on recruit survivorship
    Survivorship: % recruits alive at each sample time and after 7 days of exposure
    Water sample analysis: Nitrogen, Phosphorus, Carbon, Pigments, Bacterial
    community (454 sequencing)
    Sediments
    Recruits
    125 vials
    Control 0.1 OC% 0.3 OC% 0.9 OC%

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  13. Experiment 2: Effects of organically enriched sedimentation on recruit survivorship
    Time x enrichment interaction not significant
    p<0.05 p<0.05
    Enriched sediments can damage recruits of P. damicornis in less than 2 days
    Survivorship
    Exposure time (hours) Enrichment (OC%)

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  14. Experiment 2: Effects of organically enriched sedimentation on recruit survivorship
    Enriched sediments have long-term impacts on recruits of P. damicornis
    even when removed after a couple of hours
    Survivorship 7 days after exposure
    p<0.05
    Exposure time (hours)

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  15. Conclusions
    ü Survivorship of coral recruits and ultimately their abundance and
    distribution are negatively impacted by:
    - suspended sediments
    - organically enriched sediments
    ü Benthic habitats exposed to excessive turbidity due to river run-
    off may be sub-optimal for corals.

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  16. Questions and
    suggestions are appreciated
    Thanks!

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